Våtspinning

Våtspinning, or wet spinning, is a fiber production method in which a polymer solution or slurry is extruded through a spinneret into a coagulation bath. In the bath, the solvent diffuses out and a non-solvent diffuses in, causing the polymer to precipitate as a continuous filament. The formed fiber is then drawn, washed to remove residual solvent and bath chemicals, neutralized if needed, and dried. This technique is used for polymers that dissolve in solvents but cannot be melted to form fibers, making it distinct from melt spinning and some forms of dry spinning.

The process is widely used for cellulose-based fibers such as viscose rayon and cuprammonium rayon, where the cellulose is dissolved in a chemical solvent and extruded into a bath that regenerates cellulose and solidifies the filament. It is also employed for other polymers that form fibers from solution, such as polyacrylonitrile (PAN) and polyvinyl alcohol (PVA) in appropriate coagulation baths. Variants include dry-jet wet spinning, where a short air gap between the spinneret and the coagulation bath helps orient the polymer and improve tenacity before coagulation.

Key steps in production include preparing and filtering the dope, extruding through a spinneret into a coagulation bath, drawing or stretching the filament to set strength, and subsequent washing, neutralization, and drying. Post-treatment may involve finishing steps to improve luster or dyeability. Environmental and economic factors are important, as bath chemistry must be controlled, and effluents recycled or treated to minimize impact.